1. Field of the Invention
The present invention relates to a semiconductor device in which a concave portion (including a penetration hole) is formed in a support substrate on which a semiconductor circuit is formed, by using a sandblast method, and a method of manufacturing the same.
2. Description of the Related Art
For example, when a recording head of a thermal inkjet printer is manufactured, a heater (heating resistor) material is laminated on a silicon substrate in which a driver circuit has been formed. Further, a cavity as an ink room for each pixel and an orifice nozzle as a discharge opening of ink are formed on the heater. Since the ink is supplied from the rear side surface of the silicon substrate, an ink supply hole (a penetration hole) which penetrates the silicon substrate is formed.
Generally, the above ink supply hole is formed from both side surfaces of the silicon substrate by using the sandblast method in view of a hole forming speed. In the sandblast method, as known well, a region except for a region to be dug is masked and then a particle with a small size, such as alumina, is blasted to a semiconductor device with a semiconductor wafer state at a predetermined rate. Thus, the silicon substrate and the structure formed thereon are mechanically removed.
By the way, in the sandblast method, the particle with a small diameter is blasted by a dry air. Thus, static electricity is produced by the friction between the particle and the air.
Therefore, there is the following problem in the case of a semiconductor (silicon) device in which the concave portion (including the penetration hole) has to be formed in the support substrate by the sandblast method. That is, since the statically electrified particle collides with the silicon device, the silicon device is electrified. Thus, there may be a case where electrostatic breakdown of the silicon device is caused due to this electrification.
An object of the present invention is to provide a semiconductor device in which the problems with the above related art are solved and a concave portion (including a penetration hole) is formed by a sandblast method in a support substrate on which a semiconductor circuit is formed, without causing the electrostatic breakdown, and a method of manufacturing the semiconductor device.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor device in a state of a chip, wherein the chip has a support substrate in which at least one concave portion is formed and a metal film which is formed in a region including a circumferential portion of the concave portion and an outside of the circumferential portion on the support substrate, wherein and the metal film formed in the circumferential portion of the concave portion and a vicinity thereof is extended to an end of the support substrate.
Preferably, the metal film is formed on at least one of a front side surface and a rear side surface of the support substrate.
Preferably, the semiconductor device is a recording head of a thermal inkjet printer.
Also, according to a second aspect of the present invention, there is provided a semiconductor device in a state of a wafer, wherein the wafer has at least two chips, each of the at least two chips has a support substrate in which at least one concave portion is formed and a metal film which is formed in a region including a circumferential portion of the concave portion and an outside of the circumferential portion on the support substrate, the metal film in the circumferential portion of the concave portion and a vicinity thereof is extended to an end of the support substrate, and respective metal films extended to ends of respective support substrates of the at least two chips are connected with each other through a region between the chips.
Here, the metal film is preferably formed on at least one of a front side surface and a rear side surface of the support substrate. In addition, the semiconductor device is a recording head of a thermal inkjet printer.
Also, according to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising, in a wafer in which a plurality of chips are formed, the steps of: forming a metal film on a support substrate of each of the plurality of chips at least in the vicinity of a circumferential portion of a region in which a concave portion in a corresponding chip is to be formed, the metal film being extended from the vicinity of the circumferential portion to an end of the corresponding chip, and respective metal films of the plurality of chips being connected with each other through a region between the plurality of chips; masking an entire surface of the wafer including the metal films, except for the regions of the plurality of chips in which the concave portions are to be formed, respectively; and grounding at least a portion of the metal films and forming the concave portion in each of the plurality of chips formed, respectively, on the wafer by a sandblast method.
Here, a protective film for improving an adhesion between the metal films and a material for masking the entire surface of the wafer is preferably formed on the metal films. Also, a resistance value between the metal films formed on the respective chips and a ground is preferably 50 Mxcexa9 or lower.
In addition, it is preferable that the metal film is formed on a front side surface of the support substrate and a formation of the concave portion is started from the front side surface of the support substrate. Alternatively, it is preferable that the metal film is formed on a rear side surface of the support substrate and a formation of the concave portion is started from the rear side surface of the support substrate. Alternatively, it is the metal films are formed on a front side surface and a rear side surface of the support substrate and a formation of the concave portion is started from the front side surface and the rear side surface of the support substrate.